The present invention is generally directed to the preparation of polythiophenes and uses thereof. More specifically, the present invention in embodiments is directed to processes for the generation of polythiophenes, particularly solution processable polythiophenes, which are useful as active components in microelectronic devices. Of specific interest in embodiments of the present invention are polythiophene processes, which utilize metal halide-mediated oxidative coupling polymerization.
A number of certain polythiophenes are known which may be useful as conductive or semiconductor materials in electronic device such as thin film transistors, photovoltaic cells, organic/polymer light emitting diodes, and the like. Particularly useful polythiophenes are those which are soluble in organic solvents, and can thus be processed into microelectronic components by solution processes, such as spin coating, solution casting, dip coating, screen printing, stamp printing, jet printing and the like, thereby lowering the manufacturing cost of microelectronic devices. Specifically, certain polythiophenes, which contain repeating 2,5-thienylene (also known as 2,5-thiophendiyl) units possessing long side-chains, such as alkyl, arranged in a regioregular manner on the polythiophene backbone, may be suitable for these applications. The long alkyl side-chains, while imparting enhanced solubility characteristics to the polythiophenes, may also help induce and facilitate molecular self-organization when they are positioned in a regioregular manner on the polymer backbones. In a condensed phase, such as in thin films, molecular self-organization of polymer molecules under appropriate conditions permits ordered microstructure domains, and which molecules when present in the charge transport layers of microelectronic devices could enhance their electrical performance. For example, for the polythiophene semiconductor channel layers in thin film transistors, the presence of the lamellar π-stacking microstructures has been known to lead to superior field-effect transistor properties.
Thin film transistors, which utilize solution processable organic/polymer materials and polymer composites, may also be fabricated on plastic substrates to permit low cost lightweight structurally flexible integrated circuits which may be mechanically more robust and durable. These flexible lightweight integrated circuits are useful for incorporation into electronic devices, such as large-area image sensors, electronic paper and other display media where lightweight characteristics and device structural flexibility may be very appealing. These integrated circuit elements may also find use in low-end microelectronics, such as smart cards, radio frequency identification (RFID) tags, and memory/storage devices which require mechanical durability for extended life. For these applications, the performance of the polymer semiconductor materials, such as the polythiophenes in the channel layer, is of value. Also, while different synthetic methodologies and reaction conditions may provide analytically similar polythiophenes, the electrical performance of these polythiophenes, particularly their field-effect transistor characteristics when used as semiconductor channel materials in thin film transistor devices, may be dissimilar, for example there may be variations in the field-effect.